Hinge mechanism for variable displacement compressor

ABSTRACT

By changing the inclination of a cam plate, the stroke of a piston is changed to change the discharge displacement a of compressor. A hinge mechanism is positioned between a rotating support and the cam plate. The hinge mechanism includes a guide pin, and the guide pin transfers the rotational motion of the rotating support to the cam plate and permits inclination of the cam plate. At least a part of the guide pin is hollow.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a hinge mechanism in a variabledisplacement compressor suitable for vehicle air-conditioners and aguide pin used in such a hinge mechanism.

[0002] A typical variable displacement compressor includes a housing,which includes a cylinder block, and a drive shaft, which is supportedby the housing. In the cylinder block, a plurality of bores are formedto surround the drive shaft, and a piston is located in each bore. Aswash plate is driven by on the drive shaft through a special hingemechanism such that the swash plate rotates integrally with the driveshaft and inclines with respect to the drive shaft. When the inclinationof the swash plate changes, the swash plate slides along the surface ofthe drive shaft in the axial direction.

[0003] Each piston is connected to the outer periphery of the swashplate. Rotation of the drive shaft is converted to reciprocatingmovement of the pistons, and suction and compression are performed ineach of the cylinder bores. By controlling the pressure in a crankchamber, in which the swash plate is located, the inclination angle ofthe swash plate is controlled, and the stroke of the pistons and thedischarge displacement are changed accordingly.

[0004]FIG. 9 shows one example of a hinge mechanism between a swashplate and a drive shaft. The mechanism of FIG. 9 is from JapaneseUnexamined Patent Publication No. Hei 11-93833. To a drive shaft 61 isfixed to a rotor 63 in a crank chamber 62, and a pair of support arms 64projects from the rotor 63. Guide holes 65 are formed in the supportarms 64, respectively.

[0005] In the crank chamber 62, a swash plate 66 is supported by thedrive shaft 61. To limit the weight of the swash plate 66 and to preventburning of a shoe 69, the swash plate 66 includes an aluminum basedswash plate body 67 and an iron based swash plate guide 68. The swashplate body 67 is press fitted into the swash plate guide 68. The swashplate body 67 is connected to the pistons 70 via the shoes 69, whichslide on the periphery of the swash plate body 67.

[0006] A pair of guide pins 71 extend from the swash plate 68. Eachguide pins 71 includes a spherical portion 71 a, which is received byone of the guide holes 65. The support arms 64, the guide holes 65 andthe guide pins 71 form a hinge mechanism. When the pressure in the crankchamber 62 is changed, the inclination angle of the swash plate 66 ischanged so that the stroke of the piston 70 is changed while the topdead center position of each piston 23 does not substantially change.

[0007] Essentially, two types of moments, that is, a moment due tocentrifugal force and a moment generated based on mutual relationshipsbetween the internal pressures of the cylinder bores and the pressure(crank pressure Pc) in the crank chamber 62, act on the swash plate 66,and the inclination angle of the swash plate 66 is determined based onthe balance of the moments. The mass of the guide pin 71, which form thehinge mechanism, influences the moment due to centrifugal force and actsto increase the inclination angle of the swash plate 66.

[0008] In consideration of the centrifugal force moment, an xyzcoordinate system is used in FIG. 9. A vibration axis of the swash plate66 is represented by z, and the axis of the drive shaft 61, which isperpendicular to the vibration axis z, is represented by y. An axis thatis perpendicular to both the y and z axes is represented by x. The pointof intersection of the axes is shown by an origin 0. In such aright-angled coordinate system (x, y, z), the centrifugal force momentis obtained by multiplying the product of inertia Ixy of the swash plate66 with respect to the xz plane and the yz plane by the square of theangular velocity with respect to the drive shaft 61 (refer to U.S. Pat.No. 5,573,379, which is incorporated herein by reference). Here theproduct of inertia Ixy is expressed by Ixy=∫fxy dm. The dm representsmass of a minute component which forms the swash plate.

[0009] Therefore, the larger the mass of the guide pin 71 is, thegreater the influence on the moment during high velocity rotation is.Thus, to decrease the inclination angle of the swash plate 66 duringhigh speed velocity, a high crank pressure Pc is necessary. As a result,hunting may occur in the control of the crank pressure, and wear of asealing member that seals the drive shaft 61 is more likely to occur.Further, in a clutchless type compressor, the power consumption duringminimum displacement operation is increased.

[0010] When the swash plate 67 is made of an aluminum-based metal and isfitted into an iron based guide 68, the distance from the plane of theswash plate body 67 to the spherical portion 71 a of the guide pin 71 inthe axial direction increases by about 20% compared to a compressorwhere the entire swash plate 66 is formed of an iron-based metal, toensure the press-fit strength of the swash plate 66. As a result, theinfluence of the moment increases.

BRIEF SUMMARY OF THE INVENTION

[0011] The present invention has been made in consideration of theabove-described problems. An object of the present invention is toprovide a hinge mechanism of a variable displacement compressor capableof reducing pressure in a crank chamber which is necessary for changingdisplacement at a high speed rotation, capable of suppressing theoccurrence of hunting and capable of reducing the power dissipation in aclutchless type compressor, and a guide pin suitable for the hingemechanism.

[0012] To achieve the foregoing and other objectives and in accordancewith the purpose of the present invention, a variable displacementcompressor is provided. The compressor includes a housing including acylinder bore, a piston accommodated in the cylinder bore, a drive shaftsupported by the housing, a rotating support integrally fixed to thedrive shaft, a cam plate and a hinge mechanism. The cam plate isconnected to the piston for converting rotational motion of the driveshaft to reciprocation of the piston. The cam plate inclines withrespect to the drive shaft. The stroke of the piston changes to vary thedischarge displacement of the compressor when the inclination of the camplate changes. The hinge mechanism is positioned between the rotatingsupport and the cam plate. The hinge mechanism includes a guide pin fortransferring rotation of the rotating support to the cam plate and forpermitting the inclination of the cam plate, wherein a part of the guidepin is hollow.

[0013] Other aspects and advantages of the invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0014] The invention, together with objects and advantages thereof, maybest be understood by reference to the following description of thepresently preferred embodiments together with the accompanying drawingsin which:

[0015]FIG. 1 is a cross-sectional view of a first embodiment of thepresent invention;

[0016] FIGS. 2(a), 2(b), and 2(c) are cross-sectional views of variousguide pins;

[0017] FIGS. 3(a) and 3(b) are schematic cross-sectional viewsillustrating swash plates;

[0018]FIG. 4 is a graph showing a relationship between an inclinationangle of the swash plate and moment;

[0019]FIG. 5 is a partial cross-sectional view showing a hinge mechanismof a second embodiment;

[0020]FIG. 6 is a partial plan view of the hinge mechanism of FIG. 5;

[0021] FIGS. 7(a) and 7(b) are cross-sectional views showing otherembodiments of guide pins used in the compressor of the firstembodiment, and FIG. 7(c) is a perspective view of another embodiment ofa guide pin;

[0022]FIG. 8(a) is a cross-sectional view showing another embodiment ofa guide pin used in a compressor of the second embodiment, and FIG. 8(b)is a perspective view showing a guide pin of still another embodiment;and

[0023]FIG. 9 is a partial cross-sectional view of a prior art variabledisplacement compressor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] A variable displacement compressor of a vehicle air-conditionerof a first embodiment of the invention will be described with referenceto FIGS. 1, 2, and 3.

[0025] As shown in FIG. 1, a compressor 10 includes a cylinder block 11,a front housing member 12, which is fixed to the front end of thecylinder block 11, and a rear housing member 14, which is fixed to therear end of the cylinder block 11 through a valve plate 13. The housingmembers 12, 14, the valve plate 13 and the cylinder block 11 are securedto each other with a plurality of bolts 10 a (only one shown). A crankchamber 15 is defined between the cylinder block 11 and the fronthousing member 12.

[0026] A drive shaft 16 is supported in the cylinder block 11 and thefront housing member 12 with bearings. A lug plate 17 is fixed to thedrive shaft 16 in the crank chamber 15. The lug plate 17 transmitsthrust to an internal wall surface of the front housing member 12through a thrust bearing 18.

[0027] A swash plate 19, or cam plate, includes an aluminum-based swashplate body 20 and an iron-based swash plate guide 21, and the swashplate body 20 is press fitted into the swash plate guide 21. Thus,burning between the swash plate 19 and an iron-based shoe 23 a isinhibited. Also, the weight of the swash plate 19 is limited. The swashplate guide 21 is provided with a through hole 21 a, and the drive shaft16 passes through the through hole 21 a. A hinge mechanism 22 is locatedbetween the lug plate 17 and the swash plate 19. Therefore, the swashplate 19 rotates in synchronization with the lug plate 17 and the driveshaft 16, and the swash plate 19 can incline with respect to the driveshaft 16 while sliding on the drive shaft 16 in the axial direction.

[0028] The swash plate 21 includes a counterweight 21 b at a locationthat is opposite to the hinge mechanism 22 with respect to the driveshaft 16. Between the lug plate 17 and the swash plate guide 21 a spring16 a is fitted around the drive shaft 16. The spring 16 a urges theswash plate 19 toward the cylinder block 11, that is, in the directionin which the inclination angle decreases.

[0029] A plurality of cylinder bores 11 a (only one shown in FIG. 1) isprovided in the cylinder block 11 such that the bores 11 a arepositioned at equal angular intervals. A single-headed piston 23 isfitted in each of the cylinder bores 11 a. The front openings of thecylinder bores 11 a are closed by the valve plate 13, and a compressorchamber 11 b is defined in each cylinder bore 11 a. The volume of thecompressor 11 b varies depending on the position of the correspondingpiston 23. Each piston 23 is connected to the periphery of the swashplate 19 through a pair of the shoes 23 a. Accordingly, the rotationalmotion of the swash plate 19, which is produced by the rotation of thedrive shaft 16, is converted to reciprocating motion of the pistons 23.

[0030] The drive shaft 16 is connected to an engine 25 through a powertransmission mechanism 24. The power transmission mechanism 24 may be aclutch mechanism (for example, an electromagnetic clutch), whichconnects and disconnects power transmission and is externallycontrolled. Alternatively, the power transmission mechanism 24 may be aclutchless (for example, the combination of a belt and a pulley). Thepresent embodiment has a clutchless type power transmission mechanism24.

[0031] A suction chamber 26 and a substantially annular dischargechamber 27, which surrounds the suction chamber 26, are defined in therear housing member 14. In the valve plate 13, a suction port 28, asuction valve 29, which opens and closes the suction port 28, adischarge port 30, and a discharge valve 31, which opens and closes thedischarge port 30, are formed in correspondence with each cylinder bore11 a. The suction chamber 26 and the discharge chamber 27 are connectedto each other by an external refrigerant circuit 32.

[0032] The cylinder block 11, the valve plate 13 and the rear housingmember 14 are provided with an air-supply passage 33, which connects thecrank chamber 15 and the discharge chamber 27, and a bleed passage 34,which connects the crank chamber 15 and the suction chamber 26. Acontrol valve 35 is installed on the way of the supply passage 33. Thecontrol valve 35 is similar to the control valve disclosed in JapaneseUnexamined Patent Publication No. Hei 9-268973, and includes a bellows,which moves in response to changes in the suction pressure, a solenoid,which produces electromagnetic force, and a valve mechanism, whichcontrols the degree of opening of the supply passage 33 according to thedisplacement of the bellows and the electromagnetic force of thesolenoid. The parts of the control valve 35 are not shown.

[0033] When the pressure in the suction chamber 26 is a predeterminedvalue or less, the bellows are displaced so that the supply passage 33is opened, and when the pressure in the suction chamber 26 is apredetermined value or more, the supply passage 33 is held in a closedstate. The discharge displacement of the compressor is adjusted bycontrolling the pressure (crank pressure) Pc in the crank chamber withthe control valve 35. That is, when the pressure in the suction chamber26 is relatively low, the degree of opening of the control valve 35 isincreased so that the crank pressure Pc is increased. Accordingly, theinclination angle (angle formed by a plane perpendicular to the driveshaft 16 and the swash plate 19) of the swash plate 19 is decreased sothat the stroke of each piston 23 is decreased and the dischargedisplacement is reduced. On the other hand, when the pressure in thesuction chamber 26 is relatively high, the degree of opening of thecontrol valve 35 is decreased so that the crank pressure Pc is lowered.Accordingly, the inclination angle of the swash plate 19 is increased sothat the stroke of each piston 23 is increased and the dischargedisplacement is increased.

[0034] Next, the hinge mechanism 22 will be described in further detail.The hinge mechanism 22 has two supporting arms 36 (only one is shown),which extend from a rear surface of the lug plate 17, a guide hole 37formed in each of the supporting arms 36, and two guide pins 38, whichare fixed to the swash plate 19. Each guide hole 37 is cylindrical. Theguide pins 38 are parallel, and an imaginary plane that includes theaxis of the drive shaft 16 lies between the pins 38. One pin 38corresponds to each supporting arm 36. The guide pins 38 are identicalin shape and size, and are symmetrical with respect to the previouslymentioned imaginary plane.

[0035] Each of the guide pins 38 includes a shaft portion 38 a attachedto the swash plate 19 and a spherical portion 38 b formed at the distalend of the shaft portion 38 a. The spherical portions 38 b engage theguide holes 37. Each spherical portion 38 b has a larger outer diameterthan the shaft portion 38 a, and the distal end of each sphericalportion 38 b is truncated along a plane. At least a portion of eachspherical portion 38 b is hollow. Each guide pin 38 is forged by use of,for example, a header or a former.

[0036] A hollow chamber 38 c in each guide pin 38 is opened at thedistal end of the spherical portion 38 b. The shape of the hollowchamber 38 c can be appropriately selected. For example, any one of manyshapes such as a first shape, in which the hollow chamber 38 c extendsto approximately the center of the spherical portion 38 b as shown inFIG. 2(a), a second shape, in which the hollow chamber 38 c extends tothe shaft portion 38 a as shown in FIG. 2(b), and a third shape, inwhich the hollow chamber 38 c extends to the vicinity of the locationwhere the shaft portion 38 a joins with the swash plate guide 21 asshown in FIG. 2(c), can be selected. The masses of the guide pins 38shown in FIGS. 2(a), 2(b) and 2(c) decreases as indicated by thefollowing inequality: FIG. 2(a)>FIG. 2(b)>FIG. 2(c).

[0037] The shape of the swash plate 19 is like that of the swash platedisclosed in Japanese Unexamined Patent Publication, No. Hei 7-293429(U.S. Pat. No. 5,573,379). FIGS. 3(a) and 3(b) employ an xyz coordinatesystem. Additionally, a vibration axis of the swash plate 19 isrepresented by S. The axis of the drive shaft 16, is represented by y. Az-axis is perpendicular to the plane of the sheet of FIG. 3(a) and isparallel to the vibration axis S. An x-axis is perpendicular to both they and z axes. A point of intersection the x, y and z axes is defined asan origin point O. When the inclination angle of the swash plate 19starts rotation at an angular portion of zero degrees as shown in FIG.4, the product of inertia Ixy of the swash plate 19 with respect to thexy plane and the yz plane generates moment M in a direction such thatthe displacement is increased (the direction in which the inclinationangle of the swash plate 19 is increased).

[0038] The operation of the compressor is as follows.

[0039] With rotation of the drive shaft 16, the swash plate 19 rotates,and the rotation of the swash plate 19 is converted to reciprocatingmotion of each piston 23 through the shoes 23 a. As a result, in thecompressor chamber 11 b, suction, compression and discharge ofrefrigerant are sequentially repeated. Refrigerant supplied from theexternal refrigerant circuit 32 to the suction chamber 26 is drawn intothe compressor 11 b through the suction port 28. After the refrigerantis compressed, it is discharged to the discharge chamber 27 through thedischarge port 30. The refrigerant discharged to the discharge chamber27 enters the external refrigerant circuit 32 via the discharge hole.

[0040] The degree of opening of the control valve 35 is adjustedaccording to the cooling load. When the cooling load is high and thepressure in the suction chamber 26 is high, the opening degree of thecontrol valve 35 is reduced, and the pressure (crank pressure Pc) in thecrank chamber 15 is decreased as a result, which increases theinclination angle of the swash plate 19. The stroke of each piston 23 isincreased accordingly, and the compressor 10 operates with a largedisplacement. On the other hand, when the cooling load is low and thepressure in the suction chamber 26 is low, the opening degree of thecontrol valve 35 is increased and the pressure (crank pressure Pc) inthe crank chamber 15 is increased so that the inclination angle of theswash plate 19 is decreased. As a result, the stroke of the piston 23 isdecreased, and the compressor 10 operates with a small displacement.

[0041] The moment that is generated based on the relationship betweenthe internal pressure of the cylinder bores and the crank pressure Pc,the moment due to centrifugal force, and the force of the spring 16 aact on the swash plate 19, and the inclination angle of the swash plate19 is determined based on the equilibrium of these components.

[0042] The moment that is generated by rotation of the swash plate 19(the moment due to centrifugal force) is the product of inertia Ixy ofthe swash plate 19 with respect to the xz plane and the yz plane in theright-angled coordinate system (x, y, z) multiplied by the square of theangular velocity ω of the drive shaft 16.

[0043] As shown in FIG. 3(a), y axis coincides with the axis of thedrive shaft 16, the z axis is parallel to the vibration shaft S, and thex axis is perpendicular to the y axis and the z axis. When the upwarddirection of the x axis is positive and the front direction of the yaxis is also positive, the product of inertia Ixy of the swash plate isexpressed by Ixy=∫fxy dm. Here, dm is the minute mass of the swash plate19 including the guide pin. Therefore, even if the outer diameter,number and arrangement of the pistons 23, the outer diameter of theswash plate 19, the outer shape of the guide pin 38, and the rotationalspeed (angular velocity ω) are constant, the moment due to the rotationvaries depending on the distance L between the center of the sphericalportion 38 b of the guide pin 38 and the xz plane.

[0044] When the swash plate 19 is formed by press fitting the iron basedmetallic swash plate guide 21 into the aluminum based metallic swashplate body 20, to produce a large press-fit area, the distance L isincreased by about 20%, as shown in FIG. 3(a), as compared with theswash plate 19 shown in FIG. 3(b), which is an entirely iron-based swashplate. As a result, even if the shapes of the guide pins 38 are thesame, the product of inertia Ixy of the swash plate 19 of FIG. 3(a) issignificantly increased compared with the swash plate 19 of FIG. 3(b).

[0045] The moment M that is generated by rotation of the swash plate 19in the vicinity of the minimum inclination angle acts to increase theinclination angle of the swash plate 19. Thus, when the product ofinertia Ixy is large, the influence is greater at a high rotationspeeds. Therefore, to reduce the inclination angle of the swash plate19, high crank pressure Pc is required. Even if the mass of the guidepins 38 is the same as, the product of inertia Ixy of the guide pins 38becomes large when the mass of the portion spaced apart from the xyplane, the distal end portion of the guide pin 38 is larger.

[0046] On the contrary, in this embodiment, since the hollow chambers 38c are formed so that the masses of the front spherical portions 38 b ofthe guide pins 38 are decreased, even if the mass of the guide pins 38are the same, the product of inertia Ixy is smaller than that of a swashplate lacking the hollow chambers 38 c. Further, the moment M based onthe rotation of the swash plate 19 is smaller than the moment Mo of aconventional swash plate, as shown in FIG. 4. Thus, the crank pressurePc necessary for changing the inclination angle of the swash plate 19 isreduced. When the crank pressure Pc necessary for changing theinclination angle is high, the inclination angle is likely to shift by aslight variation in the compression load and hunting is likely to occureven if adjusted to a predetermined inclination angle. However, when thecrank pressure Pc necessary for changing the inclination angle isreduced, hunting is less likely to occur. This can be understood fromthe fact that the rate of change in the moment M with respect to theinclination angle of the swash plate 19 is smaller than that of themoment Mo of the swash plate provided with conventional guide pins ofFIG. 4. Reducing the mass of the guide pins 38 permits the mass of thecounterweight 21 b to be reduced, and contributes to reducing the rateof change of the rotating moment M of the swash plate 19.

[0047] This embodiment has the following effects.

[0048] (1) At least a part of the guide pin 38 is hollow. Thus, theproduct of inertia of a portion of the guide pin 38 that influences therotational moment rotation of the drive shaft 16 and the swash plate 19is decreased. As a result, the crank pressure Pc that is necessary forchanging the displacement of a compressor can be reduced at a highrotation speeds, and hunting can be inhibitted. Further, in a clutchlesstype compressor, even if the vehicle air-conditioner is off, the powerof engine is transferred to the compressor. However, at the time theinclination angle of the swash plate 19 approaches zero degree so thatpower dissipation can be decreased. Further, when a check valve isprovided downstream of the discharge port of the compressor, the valveopening pressure can be reduced and performance is consequentlyimproved.

[0049] (2) The spherical portion 38 b of the guide pin 38 and the guidehole 37 of the supporting arm 36 form the hinge mechanism 22. Therefore,sliding of the swash plate 19 on the drive shaft 16 is smoothly guidedby forming the guide hole 37 in a simple cylindrical shape or the like.

[0050] (3) When the guide pins 38 are hollowed out, the mass that hasthe greatest influence on the product of inertia Ixy is removed. Sincethe distal end of the pin 38 has a greater effect than the proximal end,the distal end is hollowed out.

[0051] (4) The hollow chamber 38 c is opened at the distal end. Thus, bychanging the depth of the hollow chamber 38 c, the product of inertiaIxy can be easily changed. Further, machining of the hollow chamber 38 cis relatively simple.

[0052] (5) The distal ends of the spherical portions 38 b of the guidepins 38 are truncated. Accordingly, the product of inertia Ixy isreduced, as compared with a conventional guide pin having a fullspherical end.

[0053] (6) The guide pin is formed by forging. Therefore, the guide pinis stronger than a pin in which the hollow chamber 38 c of the guide pin38 is formed by a cutting operation. In addition, if the guide pin ismanufactured by a header or a former, productivity is higher.

[0054] (7) The swash plate 19 is made of an aluminum based metallicswash plate body 20 and an iron based metallic swash plate guide 21.Therefore, the entire swash plate 19 is lighter than an iron-based swashplate 19.

[0055] (8) The swash plate 19 is directly supported on the drive shaft16 by the wall of the through hole 21 a. Thus, since it is not necessaryto provide a sleeve on the drive shaft 16 and a pivot shaft thatconnects the swash plate to the sleeve, the number of parts is low.

[0056] A second embodiment of the present invention will be describedwith reference to FIGS. 5 and 6. In the second embodiment, the hingemechanism 22 is different from that of the first embodiment. Otherwise,the second embodiment is basically the same as the first embodiment.Therefore, parts that are the same are denoted by the same referencenumerals, and only the differences will be explained.

[0057] As shown in FIG. 5, a sleeve 39 is fitted on the drive shaft 16and is permitted to slide on the drive shaft 16. A swash plate guide 21is pivotally supported by a pair of supporting shafts 40 (only oneshown) to the sleeve 39. The supporting shafts 40 extend perpendicularto the drive shaft 16.

[0058] The hinge mechanism 22 includes two swing arms 41 that extendfrom the swash plate guide 21 toward the lug plate 17. A supporting arm42 extends from on the lug plate 17, and a guide pin 43 connects theswing arms 41 to the supporting arm 42. The swing arms 41 surrounds thesupporting arm 42 as shown in FIG. 6. A guide hole 44 is formed in thesupporting arm 42. Each of the swing arms 41 has a mounting hole 45, theaxes of which are parallel to the supporting shaft 40. The guide pin 43is press fitted into the mounting holes 45 and fitted into the guidehole 44.

[0059] The guide hole 44 is elongated so that, even if the inclinationangle of the swash plate is changed, the top dead center position, ofthe pistons 23 do not substantially change. That is, the guide hole 44extends so that the closer the guide hole 44 is to the swash plate 19,the further it is from the drive shaft 16. The guide pin 43 is a hollowcylinder.

[0060] In the hinge mechanism 22 of this embodiment, as the guide pin 43moves along the guide hole 44, the swash plate 19 is rotated integrallywith the lug plate 17 and the sliding and inclining movements of theswash plate 19 on the drive shaft 16 are guided.

[0061] Therefore, this embodiment has the following effects in additionto the effects (1) to (7) described in the first embodiment.

[0062] (9) The guide pin 43, which is part of the hinge mechanism 22,moves along the guide hole 44, and the sliding motion and inclination ofthe swash plate 19 are guided. Therefore, the guide pin 43 can have asimple linear shape, which further simplifies manufacturing.

[0063] (10) The guide hole 44 is formed in the supporting arm 42, andmounting holes 45 are formed in the swing arms 41. Therefore, thestructure of the swash plate 19 is simple as compared to a swash platewhere the guide hole 44 is formed in the swing arm 41.

[0064] The second embodiment is not limited to the structure describedabove, and may be constructed as follows for example.

[0065] In a construction in which the spherical guide pin 38 is used, asin the first embodiment, the hollow chamber 38 c of the guide pin 38 maybe formed in the shaft 38 a of the guide pin 38, as shown in FIGS. 7(a)and 7(b). Alternatively, a hollow chamber 38 c may be formed in theguide pin 38 and a slit 38 d may be formed in the shaft portion 38 a, asshown in FIG. 7(c). In this case, the outer diameter tolerance of theshaft portion 38 a may be increased.

[0066] In the second embodiment, the guide pin 43 may be formed suchthat a partition is formed in the hollow portion 43 a as shown in FIG.8(a). Alternatively, the ends of the pin 43 may be formed by solidbodies, as shown in FIG. 8(b), instead of the simple pipe shape of FIG.5. The force on the guide pin 43 acts strongly on the ends of the guidepin 43. However, when the ends of the guide pin 43 are solid, thestrength of the guide pin 43 is improved.

[0067] In the first embodiment, the swash plate 19 may be pivotallyconnected to a sleeve 39 that is fitted on the drive shaft 16, as in thesecond embodiment, through the supporting shafts 40. Alternatively, inthe second embodiment, the swash plate 19 may be supported on the driveshaft 16 as in the first embodiment. In addition, a spherical sleeve maybe fitted on the drive shaft 16, and the swash plate 19 may be pivotallysupported on the outer surface of the spherical sleeve.

[0068] The hinge mechanisms of FIG. 1 and 6 have two joints. That is,two pins 38 couple with two holes 37 in FIG. 1, and two arms 41 formjoints in FIG. 6. Alternatively, each hinge may have just one joint.However, two sets are preferable from the viewpoints of rotationalbalance and stability in the driving power transmission.

[0069] The swash plate 19 may be made of only one kind of metal, such asan iron based metal or the like. In this case, a press-fit margin is notneeded, and the distance between the guide pin 38 and the xz plane canbe decreased. Accordingly, the product of inertia Ixy can be furtherdecreased by forming the guide pin 38 in a hollow shape. When thematerial of the swash plate 19 is the same as that of the shoe 23 a, asurface treatment (for example, aluminum spray coating) for theprevention of burning is applied to the sliding face of the shoe 23 a.

[0070] In the hinge mechanism 22 of the second embodiment, the guidehole 44 may be formed in the swing arm 41, and the mounting holes 45 maybe formed in the supporting arm 42.

[0071] The guide pin 38 may be manufactured by cutting or casting.

[0072] The present invention may be applied to a wobble type variabledisplacement compressor.

[0073] It should be apparent to those skilled in the art that thepresent invention may be embodied in many other specific forms withoutdeparting from the spirit or scope of the invention. Particularly, itshould be understood that the invention may be embodied in the followingforms.

[0074] Therefore, the present examples and embodiments are to beconsidered as illustrative and not restrictive and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalence of the appended claims.

1. A variable displacement compressor comprising: a housing including acylinder bore; a piston accommodated in the cylinder bore; a drive shaftsupported by the housing; a rotating support integrally fixed to thedrive shaft; a cam plate connected to the piston for convertingrotational motion of the drive shaft to reciprocation of the piston,wherein the cam plate inclines with respect to the drive shaft, andwherein the stroke of the piston changes to vary the dischargedisplacement of the compressor when the inclination of the cam platechanges; and a hinge mechanism positioned between the rotating supportand the cam plate, wherein the hinge mechanism includes a guide pin fortransferring rotation of the rotating support to the cam plate and forpermitting the inclination of the cam plate, wherein a part of the guidepin is hollow.
 2. The compressor according to claim 1 , wherein thehinge mechanism includes a supporting arm extending from the rotatingsupport toward the cam plate and a guide portion provided in the supportarm, the guide pin comprising: a shaft portion, which is fixed to thecam plate, and a spherical portion, which has a larger diameter than theshaft portion and is provided on the shaft portion, wherein thespherical portion engages the guide portion, and at least a part of thespherical portion is hollow.
 3. The compressor according to claim 2 ,wherein the guide pin has a hollow chamber that is open on the outerperiphery of the spherical portion, wherein the hollow chamber extendssubstantially to the center of the spherical portion.
 4. The compressoraccording to claim 2 , wherein the guide pin has a hollow chamber thatis open on the outer periphery of the spherical portion, wherein thehollow chamber extends to the shaft portion.
 5. The compressor accordingto claim 2 , wherein a part of the shaft portion is embedded in the camplate, and a part of the shaft portion is exposed from the cam plate,and wherein the guide pin has a hollow chamber that is open on the outersurface of the spherical portion, wherein the hollow chamber extendswithin the entire exposed portion of the shaft portion.
 6. Thecompressor according to claim 1 , wherein the hinge mechanism comprises:a swing arm extending from the cam plate toward the rotating support; asupporting arm on the rotating support; a guide hole formed in one ofthe swing arm and the supporting arm; and a mounting hole formed in theother of the swing arm and the supporting arm, wherein the guide pin islocated within the guide hole and the mounting hole.
 7. The compressoraccording to claim 6 , wherein the guide hole is formed in thesupporting arm and the mounting hole is formed in the swing arm.
 8. Thecompressor according to claim 7 , wherein the swing arm is a first swingarm and the mounting hole is a first mounting hole, and the compressorfurther comprises a second swing arm and a corresponding second mountinghole, the first and second swing arms being arranged on opposite sidesof the supporting arm, wherein the first mounting hole is coaxial withthe second mounting hole, and end portions of the pin, which extendbetween the swing arms and the supporting arm, are solid.
 9. Thecompressor according to claim 1 , wherein the guide pin is manufacturedby forging.
 10. The compressor according to claim 2 , wherein the distalend portion of the spherical portion is truncated.
 11. A guide pin usedin a compressor, the compressor comprising: a housing including acylinder bore; a piston accommodated in the cylinder bore; a drive shaftsupported by the housing; a rotating support integrally fixed to thedrive shaft; a cam plate connected to the piston for converting therotational motion of the drive shaft to reciprocation of the piston,wherein the cam plate inclines with respect to the drive shaft, andwherein the stroke of the piston changes to vary the dischargedisplacement of the compressor when the inclination of the cam platechanges; a hinge mechanism positioned between the rotating support andthe cam plate, wherein the hinge mechanism includes a guide pin fortransferring rotation of the rotating support to the cam plate and forpermitting the inclination of the cam plate, wherein a part of the guidepin is hollow.
 12. The guide pin according to claim 11 , wherein thehinge mechanism includes a supporting arm extending from the rotatingsupport toward the cam plate and a guide portion provided in the supportarm, the guide pin comprising: a shaft portion, which is fixed to thecam plate, and a spherical portion, which has a larger diameter than theshaft portion and is provided on the shaft portion, wherein thespherical portion engages the guide portion, and at least a part of thespherical portion is hollow.
 13. The guide pin according to claim 12 ,wherein the guide pin has a hollow chamber that is open on the outerperiphery of the spherical portion, wherein the hollow chamber extendssubstantially to the center of the spherical portion.
 14. The guide pinaccording to claim 12 , wherein the guide pin has a hollow chamber thatis open on the outer periphery of the spherical portion, wherein thehollow chamber extends to the shaft portion.
 15. The guide pin accordingto claim 12 , wherein a part of the shaft portion is embedded in the camplate, and a part of the shaft portion is exposed from the cam plate,and wherein the guide pin has a hollow chamber that is open on the outersurface of the spherical portion, wherein the hollow chamber extendswithin the entire exposed portion of the shaft portion.